Anchor insert and pickup unit for a concrete slab



March 4, 1969 P, cou oxs ET AL. 3,431,012

ANCHOR INSERT AND PICKUP UNIT FOR A CONCRETE SLAB Filed Oct. 23, 1967Sheet of s so I i 3 12 82 I a52 92 5 1 i0 5 56 Ho 62 a 62 no I 1uvvavrom I PETER D. COURTO/S GEORGE J. ER/Ksswv 74 vt: no 5y Z v vATT'YMarch 4, 1969 cou T ET AL. 3,431,012

ANCHOR INSERT AND PICKUP UNIT FOR A CONCRETE SLAB Filed Oct. 23, 1967FIG. 4

lNl/ENTORS E} PETER D. COURTOI$ GEORGE J ER/KSSON March 4, 1969 p D,comm ET AL 3,431,012

ANCHOR INSERT AND PICKUP UNIT FOR A CONCRETE SLAB Filed on. 25, 1967Sheet 3 of s .1 lNVE/VTORS H'TER D. CouRro/s GEORGE J. ER/KSSO/V UnitedStates Patent 8 Claims ABSTRACT OF THE DISCLOSURE An improved anchorinsert adapted to be positioned on the foundation surface of a concreteslab form so that when concrete is poured into the form the insertbecomes embedded therein, and an improved separate pickup unit includinga torque stern which, when introduced through a hole in the concreteleading to the embedded insert and then twisted through an angle of 90,becomes interlocked with the insert. A bail on the pickup unit enablesthe latter to be hoisted for slab-elevating purposes.

The present invention involves a novel and improved anchor insert andpick-up unit and is designed for use primarily in connection with therelocating of a preformed concrete wall slab by such a hoisting andtilting operation as to shift the slab from the original horizontalposition in which it was formed to the final vertical position which itwill assume when it constitutes one wall of a concrete buildinginstallation. Specifically, the invention is concerned with an anchorinsert and pickup unit of the general type which is illustrated anddescribed in our copending U.S. patent application Ser. No. 500,- 491,filed on Oct. 19, 1965 and entitled Anchor Insert and Cable PickupTherefor, and also of the particular type which forms the subject matterof our copending US. patent application Ser. No. 569,360, filed on Aug.1, 1966 and entitled Anchor Insert and Releasable Pickup Unit Therefor.The present anchor insert and pickup unit is an improvement upon andeliminates the disadvantages of the anchor inserts and pickup units ofsaid applications.

Briefly, a combination anchor insert and pickup unit of the general typewith which the present invention is concerned is comprised of two parts,namely, an anchor insert and a cooperating releasable pickup unit. Theanchor insert is adapted to be embedded in one corner portion of thewall slab during formation of the latter and serves, in combination withsimilar anchor inserts in the other corner portions of the slab andafter hardening of the poured concrete, as a medium whereby the slab maybe detachably connected to a crane or similar hoisting mechanism to theend that the slab may be first raised while in a horizontal position andthen tilted into a vertical position adjacent to a concrete floor slabin order to form a principal component of a building or other concretestructure. The cooperating pickup unit consists of a tubular, verticallyelongated casting within which there is slidably disposed a lockingstern having a T-head at its lower end. The T-head is receivable in theanchor insert and, by imparting a twisting or turning motion to thestem, the T-head may be caused to move into releasable interlockingrelationship with respect to the anchor insert. After such interlockingof the T-head with the anchor insert, a nut which is threadedly receivedon the upper end of the stem may be tightened against the upper end ofthe casting in order to prevent release of the interlocked parts untilsuch time as the nut is subsequently loosened. Means are provided on thecasting whereby the same may be attached to the associated overheadcrane or other hoisting mechanism in order to raise the two interlockedparts, and consequently the slab, during actual hoisting and tilt-upoperations.

The novelty of the present invention resides in the improvements whichhave been effected in both the anchor insert and in the cooperatingreleasable pickup unit as related to the anchor insert of ouraforementioned patent application Ser. No. 500,491 and the pickup unitof our aforementioned patent application Ser. No. 569,360. Insofar asthe anchor insert is concerned, a novel form of molded thermoplasticcage member replaces the former two-piece separately formed cage memberfor creating within the concrete slab the hollow void which is necessaryto establish a path of entry for movement of the T-head into theconfines of the anchor insert for lock ing purposes. Insofar as thepickup unit is concerned, a substantially complete redesigning of thisunit eliminates the various disadvantages of the pickup unit of saidcopending patent application Ser. No. 569,360. Included in theredesigning is a novel form of securing nut and seat therefor whichobviates the condition of binding of the parts when the slab with whichthe assembly is associated is lifted, the nut and its seat beingself-aligning so that proper seating of the nut will always be attainedand the locking stem will at no time be subjected to lateral stressestending to dislodge the nut from its seat, the only stresses which areapplied to the stem being truly longitudinal ones.

Numerous other improvements distinguish the present anchor insert andpickup unit from their respective predecessors and among these is theprovision of a novel spring biasing means for effecting a detent actionbetween the T-head of the pickup unit and its locking seat on the anchorinsert, such biasing means being in the form of a spring which isentirely concealed within the T-head of the locking stem and is,therefore, shielded from contamination by foreign particles or objectswhich, otherwise, might become lodged between adjacent springconvolutions and thereby foul the operation of the biasing means.

The provision of an anchor insert and pickup unit such as outlined aboveand possessing the stated advantages constitutes the principal object ofthe present invention. Other objects and the various advantages andcharacteristics of the invention, not at this time enumerated, willreadily suggest themselves as the nature of the invention is betterunderstood from a consideration of the following detailed description.

The invention consists in the several novel features which arehereinafter set forth and are more particularly defined by the claims atthe conclusion hereof.

In the accompanying three sheets of drawings forming a part of thisspecification, one illustrative embodiment of the invention is shown.

In these drawings:

FIG. 1 is a top perspective view of the anchor insert component or partof the improved anchor insert and pickup unit constituting the presentinvention;

FIG. 2 is a bottom perspective view of the improved counterpartbail-equipped pickup unit which is designed for cooperation with theanchor insert of FIG. 1;

FIG. 3 is a fragmentary side elevational view on an enlarged scaleshowing specifically the T-head construction that is employed inconnection with the pickup unit of FIG. 2;

FIG. 4 is a sectional view taken substantially centrally and verticallythrough the assembled improved anchor insert and pickup unit, andshowing the anchor insert operatively embedded and installed in aconcrete wall slab;

FIG. 5 is a vertical sectional view taken on the line 5 of FIG. 4,certain parts being left in elevation in order more clearly to revealthe nature of the invention;

FIG. 6 is a fragmentary exploded side elevational view illustrating theanchor insert and pickup unit in the positions which they assumeimmediately prior to efl'ecting the interlock between such parts;

FIG. 7 is a perspective view of the pickup unit illustrating the mannerin which it is manipulated when operatively applied to its counterpartanchor insert;

FIG. 8 is a vertical sectional view similar to FIG. 5 but showing theanchor insert in its embedded position within the poured concrete of theslab and prior to applaction thereto of the pickup unit; and

FIG. 9 is a horizontal section on the line 9-9 of FIG. 4.

Referring now to the drawings in detail and in particular to FIG. 1, theanchor insert 10 which is illustrated in this view is substantiallyidentical to the anchor insert of our aforementioned copending patentapplication Ser. 'No. 500,491 but differs therefrom only with respect tothe use of a certain molded plastic cage member in place of a formerlyused two-piece interfitting metallic cage member as will be describedpresently. Functionally, but not structurally, the two cage members areidentical. The anchor insert 10 is designed for embedment in a tilt-uptype concrete wall slab S (see FIGS. 4, 5 and 7) and is adapted, incombination with similar inserts, to form a medium whereby said slag maybe detachably connected to an overhead crane or other hoisting mechanism(not shown) in order that the slab may be raised bodily and subsequentlytilted into a vertical position adjacent to a concrete floor slab inconnection with the construction of a building or other concreteinstallation. Toward this end, the anchor insert 10 is designed forreleasable cooperation with the novel pickup unit 12 which is illustrated in detail in FIGS. 2 to 7 of the drawings.

The anchor insert 10 involves in its general organization two crossedpairs of generally parallel rod sections 14 and 16, the pairs beingarranged in tic-tac-toe fashion and welded together at their regions ofcrossing. The rod sections of each pair are fairly widely spaced apartand constitute a support for the anchor insert as a whole in order thatthe insert may rest upon the foundation or upper surface of a slab form18 (previously formed concrete floor slab) as best seen in FIGS. 4 and5. The rod sections 16 are spaced apart more closely than the rodsections 14 of the anchor insert 10 and all of the rod sectionsconstitute embedment rods which become widely distributed in theconcrete wall slab S after a concrete pouring operation over the slabform 18. The medial regions 20 of the rod sections 14 are linearlystraight and extend horizontally while the end regions thereof areinclined downwardly as at 22 and then upwardly as at 24 to provide apair of V-shaped foot portions which are covered at their apices withelastomeric sleeves 26. The latter are provided for the purpose ofcovering or shielding said metal foot portions which otherwise would:become exposed at the bottom surface of the concrete wall slab S andhence likely to leave rust marks on such surface due to corrosion ofthese metal foot portions.

The rod sections 16 of the anchor insert 10 are pro vided with invertedwide-angle V-shaped medial regions 30 which merge with linearly straighthorizontal intermediate portions 32. These intermediate portions mergewith upwardly directed reentrant hook-like portions 34. The apices ofthe inverted V-shaped medial regions 30 provide, in effect, downwardlyfacing thrust shoulders 36 which are designed for interlockingcooperation with counterpart shoulders on the associated pickup unit 12in a manner that will be set forth in detail presently.

As best illustrated in FIGS. 1, 6 and 8, the medial regions of the rodsections 16 serve to support thereon a cup-shaped cage 40 which isformed of a suitable thermoplastic moldable material and is molded insitu directly on the rod sections 16 of the anchor insert 10. Thepurpose of this cage is to create a void in the poured concrete in whichthe insert 10 is embedded, the void leading from the upper surface ofthe slab S downwardly ,into the central regions of the anchor insert soas to provide a path for entry of certain portions of the pickup unitwhen the latter is applied to the embedded anchor insert 10. The cage 40is provided with a dished bottom wall 42 (see FIG. 6) and a cylindricalside wall 4 4 through which project the V-shaped medial regions 30 ofthe two rod sections 16. Various ways or means of applying thecup-shaped cage 40 to the medial regions of the rod sect-ions 16 may beemployed and one convenient way is initially to form the bottom wallsection 42 as a separate unit at the factory, position the same within asuitable injection mold in the approximate position which it will assumein the completed anchor insert 10, and then complete the moldingoperation wherein the cylindrical side wall 44 is formed about themedial regions of the two rod sections 16. In this manner, thecup-shaped cage emerges from the mold as a one-piece member or elementand no voids are left in the vicinity of the points of entry of the rodsections 16 into the member so that when concrete pouring operations areresorted to the wet concrete is excluded from entering the cupshapedcage 40.

The pickup unit 12 of the present invention is shown in its free statein FIGS. 2 and 3, and is shown in cooperation with its counterpartanchor insert 10 in FIGS. 4 and 5. It embodies a generally tubular,normally vertically extending forging or casting '50 including a maintubular body portion '52 from the lower rim of which there extends aflat rectangular seating flange 24. Two diametrically opposite trunnions56 overhang the longitudinal side edges of the seating flange 54, areformed integrally with and project outwards in opposite directions fromthe body portion 52, and serve pivotally to support a U-shaped liftingbail 57 having parallel arms 58 which are connected together at theirproximal ends by a semi-circular bight portion 60, the arms beingprovided at their distal or outer ends with eyelets 62 which encompassthe trunnions 56 and serve pivotally to connect the bail 57 to the bodyportion of the casting 50. The bight portion 60 of the bail is designedfor cooperation with a suitable lifting hook, a fragment of which isillustrated at 64 in FIG. 4 of the drawings, the hook being associatedwith an overhead crane or other hoisting mechanism by means of which thepickup unit may be raised after it has been operatively applied to andinterlocked with the associated anchor unit 10 in the hardened concreteslab S for slab-hoisting purposes as will be set forth in greater detailsubsequently.

The casting 50 of the pickup unit 12 is formed with a. central verticalbore 70 and an enlarged counterbore 71. The pickup unit 12 comprises, inaddition to the casting 50, a normally vertically extending, elongatedtorque stem 72 which projects loosely through said bore and counterbore.The lower end of the torque stem 72 is formed with an integral T-head 74which cooperates for locking purposes with the V-shaped medial regions30 of the parallel rod sections 16 of the anchor insert 10 as will bedescribed presently. The upper end of the torque stem 72 is providedwith a transversely extending, fixedly mounted operating handle 76 bymeans of which the stem with its T-head 74 may be turned in eitherdirection. The upper and central regions of the stem 72 are formed witha comparatively coarse external or male screw thread 78 (commonly knownas a contour thread) while the remaining lower portion or region of thestem is truly cylindrical. A locking nut 80 is threadedly received onthe male or contour screw thread 78 on the stem 72 and is capturedthereon by means of the handle 76 which prevents its removal. The nut 80has a frusto-spherical bottom surface and cooperates with afrusto-spherical seat 81 which is formed at the upper rim or end of thebore 70.

As best shown in FIG. 3, the lower portion of the torque stem 72 ishollow, which is to say that it is formed with a relatively deep,axially disposed socket 82 within which there is slidably disposed agenerally cylindrical, normally vertical plunger 84. The latter has atits lower end region a flat vertical surface 86 which defines at itsupper end a shoulder 88. Such shoulder cooperates with a horizontal pin90 to form means whereby the plunger 84 is captured within the socket 82against dislodgment. The pin 90 is mounted in a transverse hole in thelower end of the torque stem 72 and'is held in place by way of a drivefit. A helical compression spring 92 is disposed within the upperportion of the socket 82 and yieldingly urges the plunger 84 to theprojected position in which it is illustrated in FIGS. 2 and 3. Asleeve-like cylindrical pilot bushing 94 loosely surrounds the torquestem 72 and is interposed between the casting 50 and the T-thread 74.The upper end of the bushing 94 is loosely received within thecounterbore 71 as clearly shown in FIG. 5, the extent of projection ofthe bushing into the counterbore being dependent upon the extent ofthreaded engagement between the torque stem 72 and the frusto-sphericalnut 80. The lower end of the bushing rests on the T-head 74 when thepickup unit 12 is not in connected relation with the anchor insert 10.It is contemplated that the bushing 94 will be made in varying lengthsin order to accommodate varying thicknesses of concrete slabs, thebushing functioning as a guide sleeve to effect proper introduction ofthe pickup unit 12 into the concrete-embedded anchor insert duringapplication of the former to the latter.

In the operation of the herein described anchor insert and pickup unit,in order to form a concrete slab such as the wall slab S, the slab formis erected in the usual manner, and at each location within the formwhere an anchor point is to be eifected in the finished slab an anchorinsert 10 with its plastic cage 40 molded in position thereon ispositioned on the form foundation 18 with the four elastomeric sleeves26 resting upon the upper surface of such foundation. An inverted,cup-shaped, concrete-excluding shield 100 which is formed of a suitableresilient plastic material is positioned in the upper rim region of thecage 40 of each insert so that it projects vertically upwardly to thelevel of the upper surface of the slab to be formed and this shieldprecludes the entrance of poured concrete into the interior of the cage40. The shield is provided with an upstanding flexible locating prong orfinger 101 on the top wall thereof which projects above the level of theupper surface of the slab to be formed. The concrete is then poured intothe form to the desired height or thickness and then subjected to theusual screeding operation to level the upper surface of the slab. Duringthe screeding operation, the flexible prongs or fingers 101 yield topassage of the screed board thereover as indicated in dotted lines and,after each prong is released, it returns to its erect condition. Theprongs serve as locating elements which enable the sleeves 100 to bedetected and removed from the hardened concrete for subsequent reuse ina succeeding installation. Removal of the sleeves 100 leaves cylindricalpassages or holes 102 in the concrete and in vertical register with thecup-shaped cages 40. The anchor inserts 10 are then ready forinterlocking cooperation with the corresponding counterpart pickup units12 for hoisting purposes, such cooperation being effected by loweringthe units 12 endwise downwardly through the cylindrical holes 102 andmanipulating the torque stems 72 in a manner that will be described indetail.

Lowering of each pickup unit 10 as described above is accomplished bythe operator who utilizes the bail 57 as a handle to align the pilotsleeve or bushing 94 with the selected hole 102 in the concrete slab S,the T-head 74 being oriented as shown in FIG. 6 so that it will passfreely between the two inverted V-shaped medial regions 30 of the rodsections 16 of the anchor insert 10 and extend into the upper end of theopen-ended cage 40. The lower end of the free floating pilot bushing 94will enter the upper rim of the cage 40 as the pickup unit 12 isprogressively lowered while the lower end of the biasing plunger 84 willengage the foundation surface 18. Thereafter, as shown in FIG. 7, theoperator will apply downward pressure to the torque stem 72 in order toforce the same downwardly against the yielding action of thespring-biased plunger 84 and cause the T-head 74 to become lowered belowthe level of the V-shaped medial regions 30 of said rod sections 16,thus compressing the spring 92. As soon as the T-head has thus clearedthese medial regions 30, the operator will turn or twist the stem 72 ina clockwise direction so as to bring the axis of the T-head intotransverse relationship with respect to the vertical planes of the rodsections 16, at which time the T-head will underlie the medial regions30 of the rod sections 16 so that, upon release of the stem 72, thespring-biased plunger 84 will raise the torque stem 72 to the positionwherein it is illustrated in FIGS. 4 and 5 with the upper faces of theT-head on each side of the stem 72 bearing upwardly against the medialregions 30 of the rod sections 16.

In order to maintain such interlocking relationship between the T-head74 and the rod sections 16, recesses 110 are formed in the end portionsof the upper side of the T-head, the extreme apices of the V-shapedmedial portions 30 of the rods 16 seating within these recesses aftermanual pressure on the stem 72 has been discontinued. The recesses 110establish lift shoulders which are designed for engagement with thedownwardly facing thrust shoulders that are established by the apices ofthe V- shaped medial regions 30. It is to be noted at this point that,as illustrated in FIG. 9, the cross sectional shape of the torque stem72 immediately above the T-head 74 is non-circular, the lower region ofthe stem being provided with two oppositely disposed flats 112 which,when the T-head 74 is disposed below the level of the medial regions 30of the rod sections 16, are adapted to engage the sides of said medialregions and limit the extent of clockwise turning movement of which thetorque stem 72 is capable. Similarly, two oppositely disposed flats 114on the lower region of the torque stem limit the extent ofcounterclockwise turning movement of which the stem is capable. Theflats 114 are positioned at right angles to the flats 112 and form withthe latter two diametrically opposite square corners, the other twocorners being rounded or convexly curved as shown in FIG. 9. The fourflats 112 and 114 coact to restrict the angular turning movement of thetorque stem 72 to approximately 90 when the T-head is below the level ofthe medial regions 30 of the rod sections 16 so that the operator maynot inadvertently overrun the proper locking position of the T- head andalso so that he may not overrun the release position of the T-head whendisconnecting the pick-up unit 12 from the embedded anchor insert 10.

At such time as the interlocking relationship between the T-head 74 andthe rod sections 16 has been established, the operator will then screwthe frusto-spherical nut downwardly on the stem 72 in order to draw thelatter upwardly under tension and positively lock the T-head in positionagainst dislodgment. The nut, in addition to serving as a lockingelement, further serves as a reaction member to assimilate the upwardthrust of the casting 50 when the latter is lifted upwardly by the bail57 under the influence of the aforementioned overhead crane or otherhoisting mechanism. At such time as the crane hook 64 has been attachedto the bail 58 and hoisting operations have commenced, the stem 72 andthe nut 80 will assimilate the entire downward pulling force of theanchor insert 10 and the mass of hardened concrete wall slab S which isserved by the particular involved embedded anchor.

After the slab S has been hoisted to the vertical position which itassumes in the wall installation, release of the interlocking connectionbetween the pick-up unit 12 and the anchor insert 10 may be effected bbacking off of the nut 80 to such an extent that downward pressure uponthe torque stem will permit lowering of the same against the yieldingaction of the plunger 84 so as to force the T-head out of engagementwith the medial regions of the two rod sections 16. The torque stem 72may then be rotated 90 by the operator in a counterclockwise directionso as to cause the flats 114 to engage the sides of the medial regions30 of said rod sections 16, at which time the T-head will assume anangular position of register with a narrow space existing between thesetwo rod sections, whereupon the entire lower region of the pickup unit12 may be withdrawn upwardly and axially from the anchor insert 10 andalso the hole 102 through which it was initially introduced. Removal ofthe pick-up unit 12 from the anchor insert 10 exposes the hole 102 whichmay then be filled with a suitable patching cement or be otherwiseplugged. The removed pick-up unit is thus available for reuse in asubsequent slab pickup operation in connection with a different wallinstallation.

It is to be noted that by reason of the frusto-spherical nut 80 and itscooperating frusto-spherical seat 81, slight discrepancies in pullingalignment of the hoisting chain or cable that is associated with theoverhead crane and the axis of the torque stem 72 will be accommodatedwithout danger of unequal pressure being exerted upon the upper face ofthe concrete wall slab S during hoisting operations. As shown in FIG. 5,an appreciable clearance is provided between the threaded torque stem 72and the surrounding bore 70 in the casting 50. Thus, in an instancewhere the anchor insert 10 does not seat squarely on a horizontalfoundation surface, there may be as light tilting of the torque stemafter it has become interlocked with the insert. By utilizing afrusto-spherical nut and cooperating frusto-spherical seat, suchmisalignment of the torque stem 72 may be accommodated and equalpressure of the seating flange 54 on the upper face of the concrete wallslab S will be attained. Otherwise, where unequal pressure is applied toa corner region of a freshly hardened slab, there is danger offracturing of the concrete.

The invention is not to be limited to the exact arrangement of partsshown in the accompanying drawings or described in this specification asvarious changes in the details of construction may be resorted towithout departing from the spirit or scope of the invention. Therefore,only insofar as the invention is particularly pointed out in theaccompanying claims is the same to be limited.

Having thus described the invention what we claim as new and desire tosecure by Letters Patent is:

1. In combination, an anchor insert adapted for embedment in a concreteslab and a cooperating pickup unit therefor, said anchor insertcomprising a concrete-excluding cage across and through which thereextends a pair of parallel rods defining downwardly facing spaced apartthrust shoulders, said cage presenting an open upper rim, said pickupunit comprising a tubular body having a flat underneath surface adaptedto be positioned on the upper surface of the slab and also having formedtherethrough a central vertical bore designed for vertical register withsaid open upper rim of the cage when the tubular body is in position onthe slab, a vertical threaded torque stem projecting completely andloosely through said bore and provided with a T-hcad at its lower end,said T-head defining a pair of upwardly facing lift shoulders disposedon opposite sides of the stem and designed for interlocking engagementwith said downwardly facing thrust shoulders when the stem is projectedthrough said open rim to an extent sufiicient to project the T-headbelow the level of and between said parallel rods and then turnedthrough an angle of approximately the upper rim of said bore beingflared to provide a frusto-spherical seat, a frustospherical nutthreadedly received on the upper region of said stem, designed formating engagement with said seat, and adapted when tightened to draw thestem upwardly to thus pull the lift shoulders hard against said thrustshoulders, and a bail pivoted to said tubular body and forming meanswhereby the pickup unit may be attached to an overhead hoistingmechanism.

2. The combination set forth in claim 1 and wherein said cage is in theform of a relatively deep cup-shaped shell of molded plastic materialand has a cylindrical side wall which establishes said open upper rim,said parallel rods projecting through said side wall in chordal fashionand having the cage side wall bonded thereto at the points of entry ofthe rods where the latter project through said side wall.

3. The combination set forth in claim 1 and including, additionally, acylindrical pilot bushing loosely surrounding said torque stem,interposed between the tubular body and the T-head, and adapted forprojection through a preformed hole in the slab in register with theopen upper rim of the cage.

4. The combination set forth in claim 3 and wherein said bore in thetubular body has associated with it an enlarged counterbore which opensdownwardly and is adapted to receive the upper end of the pilot bushingwhen the frusto-spherical nut is tightened against its cooperatingfrusto-spherical seat.

5. The combination set forth in claim 1 and wherein the lower region ofthe torque stem is formed with a vertically disposed elongated axialsocket which faces downwardly and projects completely through theT-head, and the pickup unit embodies, additionally, a biasing plungerslidable in said socket and projecting downwardly below the lower end ofthe T-head, spring means yieldably biasing said plunger to its projectedposition, and interengaging means on the plunger and torque stern forpreventing withdrawal of the plunger from said socket.

6. The combination set forth in claim 5 and wherein the interengagingmeans comprises a shoulder on the plunger and a cross pin projectingacross said socket and engageable with the shoulder on the plunger.

7. The combination set forth in claim 1 and including, additionally,means effective when said torque stem is projected between said parallelrods for limiting the extent of turning movement of which the stem iscapable to a maximum 90.

8. The combination set forth in claim 7, wherein said means for limitingthe extent of turning movement of the stem comprises a pair of shoulderson the torque stem, one of which is engageable with one of said parallelrods to limit turning of the stem in one direction, and the other ofwhich is engageable with the other parallel rod to limit turning of thestem in the opposite direction.

References Cited UNITED STATES PATENTS 1,933,536 11/1933 Awbrey ......s52-707 2,794,336 6/1957 :Ballou 52707 3,124,385 3/1964 Neptune 52-l25ANDRES H. NIELSEN, Primary Examiner.

US. Cl. X.R.

